"All these bitches screaming that 2pac back #THUGLIFE," Rihanna said in a message underneath her photo, quoting a line from the song "Tupac Back," which was released by rappers Rick Ross and Meek Mill in mid-June 2011 on what would have been Shakur's 40th birthday.

The late rapper's "Thug Life" tattoo stood for "The Hate U Give Little Infants (Expletive) Everybody." Like him, Rihanna has several tattoos all over her body, including on her neck, wrist and back.

In another photo posted on her Twitter page around the same time, the singer is seen lying on her stomach on a table, holding a beer bottle, as a man bends over her back. His face is not shown. Rihanna wrote under the picture: "Tat my (expletive) name on u girl so I know its real!!! #MINE"

The sentence is a lyric from "Free Spirit," a song released last year by hip hop singer Drake, Rihanna's longtime friend and collaborator, that also features Ross.